Embodiments of the present disclosure relate generally to components with variable magnetization. More particularly, the disclosure relates to methods of making components with variable magnetization using selective nitrogenation and the components made thereof.
Magnetic materials used in electric machines generally serve multiple functions. For example, they may provide efficient coupling of magnetic fluxes to complementary poles across an air gap in the electric machines. Soft magnetic materials of the magnetic components may also bear a significant fraction of the mechanical and structural loads of the electric machine. Sometimes, there may be tradeoffs between efficient magnetic utilization of the material and mechanical load bearing capability of the magnetic materials. Therefore, it is desirable to have a material that can avoid the trade-offs between efficiency and operability of the electric machines by locally controlling the magnitude of the saturation magnetization of the soft magnetic material, used in electric machines.
A range of ferrous based soft magnetic compositions may be austenitized by a combination of processes to form regions of low permeability and saturation magnetizations. Characteristics of these materials can be changed by doping or otherwise selectively introducing species into the materials, for example, nitrogen. Selective nitrogenation of the magnetic materials is typically achieved by using ceramic masks. However, ceramic masks may pose several technical and process challenges. For example, stresses may be generated at the interfaces between the ceramic masks and the magnetic components, ceramic masks may require multiple and complex deposition steps, and the ceramic masks typically require removal of the ceramic barrier layers after the nitrogenation, which can add complexity and cost to the overall process. Further, ceramic masks may be difficult to remove, and typically involve chemical and/or mechanical etching of the mask, which can damage the underlying material. Thus, there is a need for improved methods of selective nitrogenation of magnetic materials.